The concept and advantages of foamed plastics material have been well known to the industry for many years and a great many attempts have been made through a variety of methods and means for forming and molding such material. The strength, lightness and economy of such plastics material are all well known but while many methods have been proposed for creating and molding such material, all of them insofar as I am aware have presented a variety of problems which have not yet been wholly solved. In some instances where gas emitting solid material is premixed with plastic pellets, the operation is expensive, both as a result of the cost of the gas emitting material as well as the cost of such premixing. In some cases, as where gas is introduced at a substantially constant pressure and in a continuous flow into a stream of plasticated plastics material, particularly if the latter is itself at a variable or pulsating pressure, the voids in the foam are of variable size and in some places may even be greatly oversize or entirely lacking.
Therefore, the purposes of the present invention include:
1. To provide apparatus of relatively simple structure which will create and deliver for appropriate shaping a plastic foam having voids of substantially uniform size having a high level of uniformity in size and distribution.
2. To provide apparatus, as aforesaid, which will involve minimum cost and only relatively simple modification in applying same to a wide variety of presently known plastics injection machines.
3. To provide apparatus, as aforesaid, which will utilize a purely gaseous supply for creating the desired foam and will eliminate the expense and inconvenience of using liquid or solid gasifiable material requiring premixing thereof with the plastics material.
4. To provide apparatus, as aforesaid, which will minimize the likelihood of leakage of gas from the machine.
Other objects and purposes of the invention will be apparent to persons acquainted with operations of the type involved here upon inspection of the following drawings and reading of the accompanying specification.